Synthesis and structural characterization of the dichloride complex formed by carboxy-functionalized Cu(diazacyclam)²⁺ cation and its heterometallic coordination polymer with CdCl₂

The asymmetric unit of the complex [3,10-bis-(3-carb-oxy-prop-yl)-1,3,5,8,10,12-hexa-aza-cyclo-tetra-decane-κ⁴ <i>N</i> ¹,<i>N</i> ⁵,<i>N</i> ⁸,<i>N</i> ¹²]di-chlorido-copper(II), [CuCl₂(C₁₆H₃₄N₆O₄)] or [Cu(H₂ <i>L</i>)Cl₂] (<b>I</b>), consists of a centrosymmetric macrocyclic Cu^II dication and a chloride anion. The components of the heterometallic compound poly[[aqua-[μ₃-3,10-bis-(3-carb-oxy-prop-yl)-1,3,5,8,10,12-hexa-aza-cyclo-tetra-dec-ane-κ⁴ <i>N</i> ¹,<i>N</i> ⁵,<i>N</i> ⁸,<i>N</i> ¹²:κ² <i>O</i>,<i>O</i>':κ² <i>O</i>'',<i>O</i>''']-μ-chlorido--copper(II)cadmium(II] 1.25-hydrate], {[CuCd(C₁₆H₃₂N₆O₄)Cl₂(H₂O)]·1.25H₂O} _<i>n</i> or {[CuCd(<i>L</i>)(H₂O)Cl₂]·1.25H₂O} _<i>n</i> (<b>II</b>) are [Cu(<i>L</i>)(H₂O)] moieties coordinated to CdCl₂ units <i>via</i> the deprotonated carb-oxy-lic groups of the macrocycle, and four water mol-ecules of crystallization with partial occupancies. In each compound, the Cu^II ion coord-inates in the equatorial plane by the four secondary N atoms of the macrocyclic ligand, which adopts the most energetically stable <i>trans</i>-III conformation, and two mutually <i>trans</i> axial ligands in tetra-gonally elongated <i>trans</i>-CuN₄Cl₂ and <i>trans</i>-CuN₄(H₂O)Cl octa-hedral geometries in <b>I</b> and <b>II</b>, respectively. The coordination environment of the Cd^II ion in <b>II</b> is a CdO₄Cl₂ distorted octa-hedron formed by two bidentately coordinated deprotonated carb-oxy-lic groups of different macrocycles and two chloride anions, one of which displays a μ₂-bridging function between the Cu^II and Cd^II ions. The extended structures of both complexes are distinctly lamellar. In particular, due to hydrogen-bonding inter-actions with participation of carb-oxy-lic groups, chloride atoms and secondary amino groups of the macrocycle, the electro-neutral mol-ecules in crystal of <b>I</b> are arranged in chains running in the [101] direction; hydrogen bonding between the chains leads to layers parallel to the (101) plane. In crystal of <b>II</b>, polymeric chains running along the [101] direction are joined into layers parallel to the (101) plane <i>via</i> formation of Cu-Cl bonds and inter-chain hydrogen bonds. There are no hydrogen-bonding inter-actions between the layers and the three-dimensional structure of <b>II</b> is based on the weak C-H⋯O and C-H⋯Cl contacts.